1. Field of the Invention
The present invention relates generally to a gas turbine and more particularly to a gas turbine in which a blade ring, especially of first and second stages, is improved in shape so as to have less thermal influence and is cooled with less thermal expansion and uniform deformation by steam whose temperature, pressure and flow rate are controlled, so that a clearance at a moving blade tip is reduced in operation, thereby enhancing gas turbine performance.
2. Description of the Prior Art
FIG. 20 is a cross sectional view showing an interior of a representative gas turbine in the prior art. In FIG. 20, numeral 100 designates an outlet of a combustor transition piece, from which a high temperature combustion gas flows out. Numeral 101 designates a gas path, in which four stages of stationary blades 1C, 2C, 3C, 4C are arranged in an axial direction of the turbine. The stationary blades 1C, 2C, 3C, 4C are connected fixedly to blade rings 102, 103, 104, 105, respectively, via respective outer shrouds. Each of the stationary blades 1C, 2C, 3C, 4C includes a plurality of blades arranged in a circumferential direction of the turbine along respective inner walls of the blade rings 102, 103, 104, 105. Also, moving blades 1S, 2S, 3S, 4S are arranged in the axial direction alternately with the stationary blades 1C, 2C, 3C, 4C and each of the moving blades 1S, 2S, 3S, 4S is connected fixedly to a rotor 200 and includes a plurality of blades arranged in the circumferential direction around the rotor 200.
In the gas turbine of the above-mentioned construction, cooling of the blade is usually done by air such that the stationary blade is fed with cooling air from the blade ring side and the moving blade is fed with cooling air from the rotor side. Along with recent higher temperature gas turbines, however, is a tendency to employ a cooling system using steam. Also, at the time of start-up of the gas turbine, while there is maintained a predetermined clearance between a moving blade tip and a blade ring, the blade ring is still cold to shrink in the rise time and, on the other hand, the rotor and the moving blade are heated earlier. Hence, the clearance at the moving blade tip becomes smaller and a risk of contact in operation becomes higher. Accordingly, the clearance must be set appropriately taking this risk into consideration. If this clearance is too broad, it will reduce the gas turbine performance. Thus to make the clearance between the moving blade tip and the blade ring as small as possible is an effective means to enhance the gas turbine performance. But the present status is that such a countermeasure is not sufficiently established yet in the field of the industrial gas turbine.
As mentioned above, in the conventional industrial gas turbine, it is usual that cooling air is led into the gas turbine stationary blade, moving blade, rotor, etc. for cooling thereof. But, in the recent tendency to employ a higher temperature gas turbine, a steam cooling system is being used in place of the air cooling system. In such a gas turbine, the clearance between the moving blade tip and the blade ring changes due to thermal influences in the operation, beginning from the start-up time. The predetermined clearance at the start-up time becomes the minimum clearance state caused by a thermal elongation difference between the blade ring and the moving blade in the rise time, so that contact may arise, inviting a dangerous state unless an appropriate setting of the clearance is ensured. Also, if the clearance is too large in operation, it will invite a reduction in the gas turbine performance, so the appropriate setting of the tip clearance of the moving blade becomes necessary. For this purpose, it is preferable to make the tip clearance less changeable by heat as well as to make the tip clearance optimally controlled so as not to cause contact but, while such control is being variously studied, it is the present status that a sufficient art therefor is not established yet in the field of the industrial gas turbine.
In view of the mentioned problem in the prior art, it is an object of the present invention to provide a gas turbine in which a gas turbine blade ring is improved in structural shape so as to have less thermal influence and to have the blade ring made with a cooling system using steam in which the temperature, pressure and flow rate are controlled so that a clearance between a moving blade tip and the blade ring may be optimally set.
In order to achieve the mentioned object, the present invention provides the following (1) to (15):
(1) A gas turbine comprises a moving blade and a blade ring confronting a tip of the moving blade. A cooling passage is provided in the blade ring and an auxiliary boiler and a steam supply source connecting to a steam turbine bottoming cycle are connected to the cooling passage. Steam of the auxiliary boiler or the steam supply source flows into the cooling passage for cooling the blade ring and the steam having cooled the blade ring is recovered. Accordingly, a clearance between the tip of the moving blade and the blade ring is reduced.
(2) A gas turbine comprises a moving blade and a blade ring confronting a tip of the moving blade as well as a combustor and a transition piece contained in the combustor. A cooling passage is provided in the blade ring so that steam of a steam supply source flows into the cooling passage for cooling the blade ring and the steam having cooled the blade ring is flown into the transition piece via a combustor transition piece connection portion for cooling a wall interior of the transition piece. The steam having cooled the wall interior of the transition piece is recovered into the steam supply source. Accordingly, a clearance between the tip of the moving blade and the blade ring is reduced.
(3) A gas turbine comprises a moving blade and a blade ring confronting a tip of the moving blade as well as a combustor and a transition piece contained in the combustor. A cooling passage is provided in the blade ring so that steam of a steam supply source flows in parallel into the cooling passage for cooling the blade ring and into the transition piece via a combustor transition piece connection portion for cooling a wall interior of the transition piece. The steam having cooled the blade ring and the wall interior of the transition piece is recovered into the steam supply source. Accordingly, a clearance between the tip of the moving blade and the blade ring is reduced.
(4) A gas turbine comprises a first stage stationary blade and a first stage moving blade and a blade ring confronting a tip of the first stage moving blade as well as a combustor and a transition piece contained in the combustor. A blade ring cooling passage is provided in the blade ring and a stationary blade cooling passage is provided in the first stage stationary blade so as to connect to the blade ring cooling passage. Steam of a steam supply source flows into the blade ring cooling passage for cooling the blade ring and the steam having cooled the blade ring flows into the stationary blade cooling passage for cooling the first stage stationary blade. The steam having cooled the first stage stationary blade flows into the transition piece via a combustor transition piece connection portion for cooling a wall interior of the transition piece and the steam having cooled the wall interior of the transition piece is recovered into the steam supply source. Accordingly, a clearance between the tip of the first stage moving blade and the blade ring is reduced.
(5) A gas turbine comprises a first stage stationary blade, a first stage moving blade, a blade ring confronting a tip of the first stage moving blade as well a combustor and a transition piece contained in the combustor. A blade ring cooling passage is provided in the blade ring and a stationary blade cooling passage is provided in the first stage stationary blade so as to connect to the blade ring cooling passage. Steam of a steam supply source flows in parallel into the blade ring cooling passage for cooling the blade ring and into the stationary blade cooling passage for cooling the first stage stationary blade. The steam having cooled the first stage stationary blade flows into the transition piece via a combustor transition piece connection portion for cooling a wall interior of the transition piece. The steam having cooled the blade ring and the wall interior of the transition piece is recovered into the steam supply source. Accordingly, a clearance between the tip of the first stage moving blade and the blade ring is reduced.
(6) A gas turbine as mentioned in (2) above can have the following additional aspects. The blade ring is a blade ring confronting a tip of a first stage moving blade, the combustor is a plurality of combustors arranged in a turbine circumferential direction, there are provided in the blade ring a plurality of blocks protruding in a turbine axial direction from positions of the blade ring corresponding to positions of the plurality of combustors and, in each of the plurality of blocks, there is provided a U-shaped passage formed by turbine axial directional and circumferential directional passages. Steam flows into the U-shaped passage from one end of the U-shaped passage for cooling the blade ring and flows out of the other end of the U-shaped passage. The steam having cooled the blade ring is supplied into the transition piece via the combustor transition piece connection portion.
(7) A gas turbine as mentioned in (2) above can also have the following additional aspects. The blade ring comprises a first blade ring confronting a first stage moving blade and a second blade ring confronting a second stage moving blade. The cooling passage comprises a first cooling passage formed in the first blade ring and a second cooling passage formed in the second blade ring, and there are provided a turbine axial directional passage for connecting the first and second cooling passages to each other and a transition piece side passage for connecting the first cooling passage and the combustor transition piece connection portion to each other. The steam of the steam supply source flows sequentially in the second cooling passage, the turbine axial directional passage, the first cooling passage and the transition piece side passage, and is then supplied to the combustor transition piece connection portion.
(8) A gas turbine as mentioned in (7) above can have the following further aspects. The combustor transition piece connection portion comprises a transition piece cooling inlet connecting to the first cooling passage, a transition piece cooling outlet through which the steam having cooled the transition piece flows out and an outlet pipe manifold connecting to the transition piece cooling outlet.
(9) A gas turbine as mentioned in (7) above can also have the following additional aspects. Each of the first and second blade rings is formed such that upper and lower two separated semicircular portions of the blade ring are joined together at flanges provided on both side surface portions of the blade ring. There are provided a recessed portion or a protruded portion on an outer circumferential surface portion of the blade ring so as to fit to or fit in a portion of a turbine casing inner wall and another protruded portion on an inner circumferential surface portion of the blade ring so as to support a wall surface confronting the tip of the moving blade. A turbine axial directional cross sectional shape of the blade ring is approximately symmetrical relative to a turbine radial directional central axis in the turbine axial directional cross sectional shape of the blade ring.
(10) A gas turbine as mentioned in (7) above can also have the following additional aspects. Each of the first and second blade rings is formed such that two upper and lower separated semicircular portions of the blade ring are joined together at flanges provided on both side surface portions of the blade ring. In horizontal surface portions of the upper and lower semicircular portions of the blade ring so joined at the flanges, the cooling passage provided in the upper semicircular portion of the blade ring is extended so as to be inserted with a predetermined length into the cooling passage provided in the lower semicircular portion of the blade ring. A sealing material is interposed around the so-extended cooling passage of the upper semicircular portion of the blade ring.
(11) A gas turbine as mentioned in any one of (1) to (5) above can have the blade ring formed such that two upper and lower separated semicircular portions of the blade ring are joined together at flanges provided on both side surface portions of the blade ring. There are provided members, having masses substantially thermally equivalent to the flanges, on upper and lower portions of an outer circumferential surface portion of the blade ring.
(12) A gas turbine as mentioned in anyone of (1) to (5) above can have the blade ring provided with a plurality of steam inlets and steam outlets, respectively, arranged substantially evenly in vertical and horizontal directions on an outer circumferential surface portion of the blade ring.
(13) A gas turbine as mentioned in (7) above can have the blade ring be applied with a thermal shield made of a heat insulation material on its surface exposed to a high temperature space.
(14) A gas turbine as mentioned in any one of (1) to (5) above can have the blade ring provided therein with a plurality of sensors for sensing the clearance at the tip of the moving blade. The sensors are inserted from outside of a turbine casing to pass through the turbine casing and the blade ring so that sensing portions of the sensors may be exposed on an inner circumferential wall surface confronting the tip of the moving blade. There are provided a steam temperature controller arranged in a route for supplying the blade ring with steam from the steam supply source, a steam flow control valve arranged between the steam temperature controller and a steam inlet of the blade ring and a control unit taking signals from the sensors for comparison with a predetermined target value and controlling the steam temperature controller and an opening of the steam flow control valve so that the clearance may approach the target value.
(15) A gas turbine as mentioned in (14) above can have the sensors be FM electrostatic capacity type sensors.
The present invention is based on the inventions mentioned in (1) to (5) above. In the invention (1), firstly at the start-up time, steam from the auxiliary boiler is supplied into the cooling passage of the blade ring so that the blade ring which is cold during the rise time is heated and the clearance at the moving blade tip is enlarged, whereby contact at the minimum clearance during the rise time can be avoided. In the ordinary operation time, steam from the steam turbine bottoming cycle is supplied into the blade ring to cool the portion of the blade ring confronting the moving blade tip and, by setting the temperature, pressure and flow rate of the steam appropriately, thermal elongation of the blade ring is controlled so that the clearance at the moving blade tip may be set correctly. Whereby the gas turbine performance is prevented from being reduced by enlargement of the clearance.
In the invention (2), the blade ring is first cooled and the clearance at the moving blade tip can be controlled appropriately. Then the steam which has cooled the blade ring flows into the combustor transition piece to flow in the high temperature wall interior of the transition piece for cooling thereof and is recovered thereafter. Thus, the control of the clearance is carried out and the cooling of the transition piece by steam is also carried out, thereby contributing to the enhancement of the gas turbine performance.
In the invention (3), steam supply to the blade ring and to the transition piece are done in parallel, and the same effect as that of the invention (2) can be obtained. Further, there is no need to provide a steam supply passage from the blade ring to the transition piece. Rather, the steam is supplied into the transition piece independently, whereby the applicability of the cooling system is broadened and an appropriate cooling system can be selected according to the type of the gas turbine.
In the invention (4), the steam first cools the blade ring and then cools the stationary blade. The steam which has been temperature-elevated by the cooling cools the transition piece, which is a high temperature portion. Thus, not only the blade ring is cooled and the clearance at the moving blade tip is controlled, but also the stationary blade and the transition piece are cooled, thereby contributing to the enhancement of the gas turbine performance.
In the invention (5), steam supply to the blade ring and the stationary blade, and that to the transition piece, are done in parallel, and the same effect as that of the invention (4) can be obtained. Further, the cooling system is made such that the steam supply to the transition piece can be done by a separate system, whereby the applicability of the cooling system is broadened, and an appropriate cooling system can be selected according to the type of the gas turbine.
In the invention (6), the blade ring of the invention (2) is only the blade ring of the first stage, which receives the severest thermal influence, and the cooling passage is formed by the U-shaped passage in each of the blocks arranged corresponding to positions of the combustors. Thereby, inflow of the cooling steam to the transition piece and outflow therefrom of the cooling steam having cooled the transition piece, both via the combustor transition piece connection portion, are facilitated, and the structure therefor can be simplified.
In the invention (7), the blade ring of the invention (2) is divided into the first and second blade rings. The first and second blade rings are provided with the first and second cooling passages, respectively. The clearances at the tips of the first stage and second stage moving blades, respectively, can thereby be controlled by the steam-cooling of the blade rings, and the performance of the gas turbine of the invention (2) can be effectively further enhanced.
In the invention (8), supply of the cooling steam into the transition piece mentioned in the invention (7) is done easily through the transition piece cooling inlet of the combustor transition piece connection portion. The cooling steam having cooled the transition piece is taken out easily through the transition piece cooling outlet so as to be collected in the outlet pipe manifold, whereby the recovery of the steam can be done easily into the steam supply source from the outlet pipe manifold.
In the invention (9), the cross sectional shape of the blade ring is approximately symmetrical relative to the radial directional central axis thereof so as to be compact in shape. The fitting of the blade ring with the turbine casing inner wall is done easily via the recessed or protruded portion, whereby the deformation quantity of the blade ring can be made smaller and equalized. Further, by making the blade ring cross sectional shape compact, the fitting portion with the turbine casing is simplified and the diameter of the turbine casing in this area can be made smaller. Also, in the invention (10), at the flange connection portion of the upper and lower semicircular portions of the blade ring, the sealing material is interposed around the extended cooling passage of the upper semicircular portion of the blade ring and thereby steam leakage in this portion can be prevented. Also, in the invention (11), the members having the thermal balancing masses substantially equivalent to the flanges on both of the side surfaces of the blade ring are provided on the upper and lower portions of the blade ring, whereby distortion of the blade ring caused by heat can be made uniform and occurrence of unusual thermal stresses can be prevented. Also, in the invention (12), the steam inlets and steam outlets of the blade ring are arranged evenly as much as possible in the vertical and horizontal directions, whereby the thermal deformation is balanced and the thermal deformation quantity is made uniform. Also, in the invention (13), the thermal shield is applied to the surface of the blade ring exposed to the high temperature gas, whereby the thermal influence given to the blade ring can be lessened.
In the invention (14), the basic inventions of (1) to (5) above are supplemented with the sensors provided circumferentially in the blade ring for sensing the clearances at the tip of the moving blade and the signals of the clearances so sensed are inputted into the control unit. The control unit compares the clearance signals so sensed with the target value, which is stored in advance, and controls the steam temperature by the steam temperature controller and also controls the opening of the flow control valve so that the clearances may approach the target value. By such control, the steam temperature, pressure and flow rate can be adjusted easily, the clearances are set to the target value, and the gas turbine performance can be prevented from being reduced. Further, in the invention (15), the FM electrostatic capacity type sensor is used, whereby the clearance can be detected precisely, even in a high temperature state, in the range of 0 to 5 mm.